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            <h2 class="toc-title">目录</h2>
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        </div><article class="page single"><h1 class="single-title animate__animated animate__flipInX">计算器——第一个Android小项目</h1><div class="post-meta">
            <div class="post-meta-line"><span class="post-author"><a href="/" title="Author" rel="author" class="author"><i class="fas fa-user-circle fa-fw" aria-hidden="true"></i>MC</a></span>&nbsp;<span class="post-category">收录于 <a href="/categories/android/"><i class="far fa-folder fa-fw" aria-hidden="true"></i>Android</a></span></div>
            <div class="post-meta-line"><i class="far fa-calendar-alt fa-fw" aria-hidden="true"></i>&nbsp;<time datetime="2017-09-09">2017-09-09</time>&nbsp;<i class="fas fa-pencil-alt fa-fw" aria-hidden="true"></i>&nbsp;约 2475 字&nbsp;
                <i class="far fa-clock fa-fw" aria-hidden="true"></i>&nbsp;预计阅读 5 分钟&nbsp;<span id="/android%E7%AC%AC%E4%B8%80%E4%B8%AA%E9%A1%B9%E7%9B%AE-%E8%AE%A1%E7%AE%97%E5%99%A8/" class="leancloud_visitors" data-flag-title="计算器——第一个Android小项目">
                        <i class="far fa-eye fa-fw" aria-hidden="true"></i>&nbsp;<span class=leancloud-visitors-count></span>&nbsp;次阅读
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        </div><div class="details toc" id="toc-static"  data-kept="">
                <div class="details-summary toc-title">
                    <span>目录</span>
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  <ul>
    <li><a href="#计算器的布局">计算器的布局</a></li>
    <li><a href="#mainactivity中的代码">MainActivity中的代码</a></li>
  </ul>
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            </div><div class="content" id="content"><h1 id="android计算器">Android计算器</h1>
<p>这是我第一个Android小项目，相信这也是大多数人的第一个小项目。
这个项目非常的简单，只有一个Activity。
首先是布局文件，这里我用的是线性布局。</p>
<h2 id="计算器的布局">计算器的布局</h2>
<p>这个布局文件中的按钮（Button）比较多。
首先是一个TextView，然后是一堆按钮。</p>
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<pre tabindex="0" class="chroma"><code class="language-xml" data-lang="xml"><span class="line"><span class="cl"><span class="cp">&lt;?xml version=&#34;1.0&#34; encoding=&#34;utf-8&#34;?&gt;</span>
</span></span><span class="line"><span class="cl"><span class="nt">&lt;LinearLayout</span> <span class="na">xmlns:android=</span><span class="s">&#34;http://schemas.android.com/apk/res/android&#34;</span>
</span></span><span class="line"><span class="cl">    <span class="na">android:orientation=</span><span class="s">&#34;vertical&#34;</span>
</span></span><span class="line"><span class="cl">    <span class="na">android:layout_width=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">    <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">    <span class="nt">&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="nt">&lt;LinearLayout</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:id=</span><span class="s">&#34;@+id/text_view&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:layout_width=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:layout_height=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:layout_weight=</span><span class="s">&#34;2&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="nt">&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;TextView</span>
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</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:background=</span><span class="s">&#34;#ffffff&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textColor=</span><span class="s">&#34;#e51c23&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:gravity=</span><span class="s">&#34;bottom|right&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;30sp&#34;</span> <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/LinearLayout&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="nt">&lt;LinearLayout</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:id=</span><span class="s">&#34;@+id/button_1line&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:layout_width=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:layout_height=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:orientation=</span><span class="s">&#34;horizontal&#34;</span><span class="nt">&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_left&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;(&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;30sp&#34;</span> <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_right&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_marginLeft=</span><span class="s">&#34;-8dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;)&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;30sp&#34;</span> <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_clear&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_marginLeft=</span><span class="s">&#34;-8dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;C&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;30sp&#34;</span> <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_back&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_marginLeft=</span><span class="s">&#34;-8dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;＜Del&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textAllCaps=</span><span class="s">&#34;false&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;25sp&#34;</span> <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/LinearLayout&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="nt">&lt;LinearLayout</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:id=</span><span class="s">&#34;@+id/button_2line&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:layout_width=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:layout_height=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:orientation=</span><span class="s">&#34;horizontal&#34;</span> <span class="nt">&gt;</span>
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_7&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;7&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;30sp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_8&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_marginLeft=</span><span class="s">&#34;-8dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;8&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;30sp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_9&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_marginLeft=</span><span class="s">&#34;-8dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;9&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;30sp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_add&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_marginLeft=</span><span class="s">&#34;-8dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;+&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;40sp&#34;</span> <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/LinearLayout&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="nt">&lt;LinearLayout</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:id=</span><span class="s">&#34;@+id/button_3line&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:layout_width=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:layout_height=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:orientation=</span><span class="s">&#34;horizontal&#34;</span> <span class="nt">&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_4&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;4&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;30sp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_5&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;5&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_marginLeft=</span><span class="s">&#34;-8dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;30sp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_6&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_marginLeft=</span><span class="s">&#34;-8dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;6&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;30sp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_minus&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_marginLeft=</span><span class="s">&#34;-8dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;-&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;50sp&#34;</span> <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/LinearLayout&gt;</span>
</span></span><span class="line"><span class="cl">    <span class="nt">&lt;LinearLayout</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:id=</span><span class="s">&#34;@+id/button_4line&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:layout_width=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:layout_height=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:orientation=</span><span class="s">&#34;horizontal&#34;</span> <span class="nt">&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;30sp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_2&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_marginLeft=</span><span class="s">&#34;-8dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;2&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;30sp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_3&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_marginLeft=</span><span class="s">&#34;-8dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;3&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;30sp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_mul&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_marginLeft=</span><span class="s">&#34;-8dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;×&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;35sp&#34;</span> <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/LinearLayout&gt;</span>
</span></span><span class="line"><span class="cl">    <span class="nt">&lt;LinearLayout</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:id=</span><span class="s">&#34;@+id/button_5line&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:layout_width=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:layout_height=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">        <span class="na">android:orientation=</span><span class="s">&#34;horizontal&#34;</span> <span class="nt">&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_point&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;.&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;40sp&#34;</span> <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_0&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_marginLeft=</span><span class="s">&#34;-8dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;0&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;30sp&#34;</span> <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_div&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;÷&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_marginLeft=</span><span class="s">&#34;-8dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;40sp&#34;</span> <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="nt">&lt;Button</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:id=</span><span class="s">&#34;@+id/button_equals&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_width=</span><span class="s">&#34;0dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_height=</span><span class="s">&#34;match_parent&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_weight=</span><span class="s">&#34;1&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:layout_marginLeft=</span><span class="s">&#34;-5dp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:text=</span><span class="s">&#34;=&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:background=</span><span class="s">&#34;#3388FF&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="na">android:textSize=</span><span class="s">&#34;50sp&#34;</span>
</span></span><span class="line"><span class="cl">            <span class="nt">/&gt;</span>
</span></span><span class="line"><span class="cl">    <span class="nt">&lt;/LinearLayout&gt;</span>
</span></span><span class="line"><span class="cl"><span class="nt">&lt;/LinearLayout&gt;</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>接下来就是ManActivity中的代码了，当然其中主要就是一个按钮的监听，也没有什么难度。</p>
<h2 id="mainactivity中的代码">MainActivity中的代码</h2>
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<td class="lntd">
<pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kn">package</span> <span class="nn">com.example.calculatortest</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kn">import</span> <span class="nn">android.support.v7.app.AppCompatActivity</span><span class="o">;</span>
</span></span><span class="line"><span class="cl"><span class="kn">import</span> <span class="nn">android.os.Bundle</span><span class="o">;</span>
</span></span><span class="line"><span class="cl"><span class="kn">import</span> <span class="nn">android.view.View</span><span class="o">;</span>
</span></span><span class="line"><span class="cl"><span class="kn">import</span> <span class="nn">android.widget.Button</span><span class="o">;</span>
</span></span><span class="line"><span class="cl"><span class="kn">import</span> <span class="nn">android.widget.TextView</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">public</span> <span class="kd">class</span> <span class="nc">MainActivity</span> <span class="kd">extends</span> <span class="n">AppCompatActivity</span> <span class="kd">implements</span> <span class="n">View</span><span class="o">.</span><span class="na">OnClickListener</span><span class="o">{</span>
</span></span><span class="line"><span class="cl">    <span class="n">StringBuffer</span> <span class="n">sb</span> <span class="o">=</span> <span class="k">new</span> <span class="n">StringBuffer</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">    <span class="kd">private</span> <span class="n">TextView</span> <span class="n">text</span> <span class="o">=</span> <span class="kc">null</span><span class="o">;</span>   <span class="c1">// 用于显示输入和输出
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>    <span class="nd">@Override</span>
</span></span><span class="line"><span class="cl">    <span class="kd">protected</span> <span class="kt">void</span> <span class="nf">onCreate</span><span class="o">(</span><span class="n">Bundle</span> <span class="n">savedInstanceState</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">        <span class="kd">super</span><span class="o">.</span><span class="na">onCreate</span><span class="o">(</span><span class="n">savedInstanceState</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">setContentView</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">layout</span><span class="o">.</span><span class="na">simple_1</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">getSupportActionBar</span><span class="o">().</span><span class="na">hide</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">        <span class="n">text</span> <span class="o">=</span> <span class="o">(</span><span class="n">TextView</span><span class="o">)</span> <span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">text_edit</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="c1">// 数字按钮
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>        <span class="n">Button</span> <span class="n">button0</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span><span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_0</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">Button</span> <span class="n">button1</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span><span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_1</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">Button</span> <span class="n">button2</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span><span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_2</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">Button</span> <span class="n">button3</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span><span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_3</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">Button</span> <span class="n">button4</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span><span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_4</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">Button</span> <span class="n">button5</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span><span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_5</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">Button</span> <span class="n">button6</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span><span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_6</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">Button</span> <span class="n">button7</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span><span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_7</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">Button</span> <span class="n">button8</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span><span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_8</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">Button</span> <span class="n">button9</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span><span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_9</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="c1">// 功能按钮
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>        <span class="c1">// 四则运算
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>        <span class="n">Button</span> <span class="n">button_div</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span><span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_div</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">Button</span> <span class="n">button_mul</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span><span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_mul</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">Button</span> <span class="n">button_add</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span><span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_add</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">Button</span> <span class="n">button_minus</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span> <span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_minus</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="n">Button</span> <span class="n">button_back</span>  <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span><span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_back</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">Button</span> <span class="n">button_clear</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span> <span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_clear</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="n">Button</span> <span class="n">button_point</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span> <span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_point</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">Button</span> <span class="n">button_equals</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span> <span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_equals</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="c1">// 左右括号
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>        <span class="n">Button</span> <span class="n">button_left</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span> <span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_left</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">Button</span> <span class="n">button_right</span> <span class="o">=</span> <span class="o">(</span><span class="n">Button</span><span class="o">)</span> <span class="n">findViewById</span><span class="o">(</span><span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_right</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="n">button0</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">button1</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">button2</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">button3</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">button4</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">button5</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">button6</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">button7</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">button8</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">button9</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="n">button_add</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">button_minus</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">button_mul</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">button_div</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="n">button_back</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">button_clear</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="n">button_point</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">button_equals</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">        <span class="n">button_left</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="n">button_right</span><span class="o">.</span><span class="na">setOnClickListener</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">    <span class="o">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="kd">private</span> <span class="n">String</span> <span class="n">sign</span> <span class="o">=</span> <span class="s">&#34;+-*/&#34;</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">    <span class="nd">@Override</span>
</span></span><span class="line"><span class="cl">    <span class="kd">public</span> <span class="kt">void</span> <span class="nf">onClick</span><span class="o">(</span><span class="n">View</span> <span class="n">view</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">        <span class="k">switch</span> <span class="o">(</span><span class="n">view</span><span class="o">.</span><span class="na">getId</span><span class="o">())</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_1</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="n">sb</span><span class="o">.</span><span class="na">append</span><span class="o">(</span><span class="s">&#34;1&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_2</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="n">sb</span><span class="o">.</span><span class="na">append</span><span class="o">(</span><span class="s">&#34;2&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_3</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="n">sb</span><span class="o">.</span><span class="na">append</span><span class="o">(</span><span class="s">&#34;3&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_4</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="n">sb</span><span class="o">.</span><span class="na">append</span><span class="o">(</span><span class="s">&#34;4&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_5</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="n">sb</span><span class="o">.</span><span class="na">append</span><span class="o">(</span><span class="s">&#34;5&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_6</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="n">sb</span><span class="o">.</span><span class="na">append</span><span class="o">(</span><span class="s">&#34;6&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_7</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="n">sb</span><span class="o">.</span><span class="na">append</span><span class="o">(</span><span class="s">&#34;7&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_8</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="n">sb</span><span class="o">.</span><span class="na">append</span><span class="o">(</span><span class="s">&#34;8&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">toString</span><span class="o">());</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_9</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="n">sb</span><span class="o">.</span><span class="na">append</span><span class="o">(</span><span class="s">&#34;9&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_0</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="n">sb</span><span class="o">.</span><span class="na">append</span><span class="o">(</span><span class="s">&#34;0&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_back</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="k">if</span><span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">length</span><span class="o">()</span> <span class="o">&gt;</span> <span class="mi">0</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                    <span class="n">sb</span><span class="o">.</span><span class="na">deleteCharAt</span><span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">length</span><span class="o">()</span> <span class="o">-</span> <span class="mi">1</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                    <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="o">}</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_clear</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="n">sb</span><span class="o">.</span><span class="na">setLength</span><span class="o">(</span><span class="mi">0</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_add</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="k">if</span><span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">length</span><span class="o">()</span> <span class="o">&gt;</span> <span class="mi">0</span> <span class="o">&amp;&amp;</span> <span class="n">sign</span><span class="o">.</span><span class="na">indexOf</span><span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">charAt</span><span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">length</span><span class="o">()</span> <span class="o">-</span> <span class="mi">1</span><span class="o">))</span> <span class="o">==</span> <span class="o">-</span><span class="mi">1</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                    <span class="n">sb</span><span class="o">.</span><span class="na">append</span><span class="o">(</span><span class="s">&#34;+&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="o">}</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_minus</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="k">if</span><span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">length</span><span class="o">()</span> <span class="o">==</span> <span class="mi">0</span> <span class="o">||</span> <span class="n">sb</span><span class="o">.</span><span class="na">length</span><span class="o">()</span> <span class="o">&gt;</span> <span class="mi">0</span> <span class="o">&amp;&amp;</span> <span class="n">sign</span><span class="o">.</span><span class="na">indexOf</span><span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">charAt</span><span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">length</span><span class="o">()</span> <span class="o">-</span> <span class="mi">1</span><span class="o">))</span> <span class="o">==</span> <span class="o">-</span><span class="mi">1</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                    <span class="n">sb</span><span class="o">.</span><span class="na">append</span><span class="o">(</span><span class="s">&#34;-&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="o">}</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_mul</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="k">if</span><span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">length</span><span class="o">()</span> <span class="o">&gt;</span> <span class="mi">0</span> <span class="o">&amp;&amp;</span> <span class="n">sign</span><span class="o">.</span><span class="na">indexOf</span><span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">charAt</span><span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">length</span><span class="o">()</span> <span class="o">-</span> <span class="mi">1</span><span class="o">))</span> <span class="o">==</span> <span class="o">-</span><span class="mi">1</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                    <span class="n">sb</span><span class="o">.</span><span class="na">append</span><span class="o">(</span><span class="s">&#34;×&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="o">}</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_div</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="k">if</span><span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">length</span><span class="o">()</span> <span class="o">&gt;</span> <span class="mi">0</span> <span class="o">&amp;&amp;</span> <span class="n">sign</span><span class="o">.</span><span class="na">indexOf</span><span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">charAt</span><span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">length</span><span class="o">()</span> <span class="o">-</span> <span class="mi">1</span><span class="o">))</span> <span class="o">==</span> <span class="o">-</span><span class="mi">1</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                    <span class="n">sb</span><span class="o">.</span><span class="na">append</span><span class="o">(</span><span class="s">&#34;÷&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="o">}</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_point</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="k">if</span><span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">length</span><span class="o">()</span> <span class="o">==</span> <span class="mi">0</span> <span class="o">||!</span><span class="n">Character</span><span class="o">.</span><span class="na">isDigit</span><span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">charAt</span><span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">length</span><span class="o">()</span> <span class="o">-</span> <span class="mi">1</span><span class="o">)))</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                    <span class="n">sb</span><span class="o">.</span><span class="na">append</span><span class="o">(</span><span class="s">&#34;0.&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="o">}</span>
</span></span><span class="line"><span class="cl">                <span class="k">else</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                    <span class="n">sb</span><span class="o">.</span><span class="na">append</span><span class="o">(</span><span class="s">&#34;.&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="o">}</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_left</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="n">sb</span><span class="o">.</span><span class="na">append</span><span class="o">(</span><span class="s">&#34;(&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_right</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="k">if</span> <span class="o">(</span><span class="n">sb</span><span class="o">.</span><span class="na">indexOf</span><span class="o">(</span><span class="s">&#34;(&#34;</span><span class="o">)</span> <span class="o">!=</span> <span class="o">-</span><span class="mi">1</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                    <span class="n">sb</span><span class="o">.</span><span class="na">append</span><span class="o">(</span><span class="s">&#34;)&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="o">}</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="n">R</span><span class="o">.</span><span class="na">id</span><span class="o">.</span><span class="na">button_equals</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="n">String</span> <span class="n">s</span> <span class="o">=</span> <span class="n">sb</span><span class="o">.</span><span class="na">toString</span><span class="o">().</span><span class="na">replace</span><span class="o">(</span><span class="s">&#34;×&#34;</span><span class="o">,</span> <span class="s">&#34;*&#34;</span><span class="o">).</span><span class="na">replace</span><span class="o">(</span><span class="s">&#34;÷&#34;</span><span class="o">,</span> <span class="s">&#34;/&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">try</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                    <span class="n">s</span> <span class="o">=</span> <span class="n">Calculator</span><span class="o">.</span><span class="na">toSuffix</span><span class="o">(</span><span class="n">s</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="o">}</span> <span class="k">catch</span> <span class="o">(</span><span class="n">Exception</span> <span class="n">ex</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                    <span class="n">s</span>  <span class="o">=</span> <span class="s">&#34;出错&#34;</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">                <span class="o">}</span>
</span></span><span class="line"><span class="cl">                <span class="n">text</span><span class="o">.</span><span class="na">setText</span><span class="o">(</span><span class="n">sb</span> <span class="o">+</span> <span class="s">&#34;\n&#34;</span><span class="o">+</span><span class="s">&#34;=&#34;</span> <span class="o">+</span> <span class="n">s</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">                <span class="k">if</span> <span class="o">(</span><span class="n">s</span> <span class="o">!=</span> <span class="s">&#34;出错&#34;</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                    <span class="n">sb</span> <span class="o">=</span> <span class="k">new</span> <span class="n">StringBuffer</span><span class="o">(</span><span class="n">s</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="o">}</span><span class="k">else</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                    <span class="n">sb</span><span class="o">.</span><span class="na">delete</span><span class="o">(</span><span class="mi">0</span><span class="o">,</span> <span class="n">sb</span><span class="o">.</span><span class="na">length</span><span class="o">());</span>
</span></span><span class="line"><span class="cl">                <span class="o">}</span>
</span></span><span class="line"><span class="cl">                <span class="k">break</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">        <span class="o">}</span>
</span></span><span class="line"><span class="cl">    <span class="o">}</span>
</span></span><span class="line"><span class="cl"><span class="o">}</span>
</span></span></code></pre></td></tr></table>
</div>
</div><p>当然还有一个Calculator类，这个就是计算的核心代码了，这个类中用的是中缀转后缀来计算的，当然如果看不懂，可以看我的这个<a href="http://blog.csdn.net/starexplode/article/details/76098172" title="一个算数表达式的前缀中缀和后缀(可进行负数运算)" target="_blank" rel="noopener noreffer ">博客</a>：</p>
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<pre tabindex="0" class="chroma"><code class="language-java" data-lang="java"><span class="line"><span class="cl"><span class="kn">package</span> <span class="nn">com.example.calculatortest</span><span class="o">;</span>
</span></span><span class="line"><span class="cl"><span class="kn">import</span> <span class="nn">java.math.BigDecimal</span><span class="o">;</span>
</span></span><span class="line"><span class="cl"><span class="kn">import</span> <span class="nn">java.math.BigInteger</span><span class="o">;</span>
</span></span><span class="line"><span class="cl"><span class="kn">import</span> <span class="nn">java.math.MathContext</span><span class="o">;</span>
</span></span><span class="line"><span class="cl"><span class="kn">import</span> <span class="nn">java.math.RoundingMode</span><span class="o">;</span>
</span></span><span class="line"><span class="cl"><span class="kn">import</span> <span class="nn">java.util.ArrayDeque</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl"><span class="kd">public</span> <span class="kd">class</span> <span class="nc">Calculator</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="kd">public</span> <span class="kd">static</span> <span class="n">String</span> <span class="nf">toSuffix</span><span class="o">(</span><span class="n">String</span> <span class="n">input</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">        <span class="kt">int</span> <span class="n">len</span> <span class="o">=</span> <span class="n">input</span><span class="o">.</span><span class="na">length</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">        <span class="kt">char</span> <span class="n">c</span><span class="o">,</span> <span class="n">tempChar</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">        <span class="n">ArrayDeque</span><span class="o">&lt;</span><span class="n">Character</span><span class="o">&gt;</span> <span class="n">s1</span> <span class="o">=</span> <span class="k">new</span> <span class="n">ArrayDeque</span><span class="o">&lt;</span><span class="n">Character</span><span class="o">&gt;();</span>
</span></span><span class="line"><span class="cl">        <span class="n">ArrayDeque</span><span class="o">&lt;</span><span class="n">BigDecimal</span><span class="o">&gt;</span> <span class="n">s2</span> <span class="o">=</span> <span class="k">new</span> <span class="n">ArrayDeque</span><span class="o">&lt;&gt;();</span>
</span></span><span class="line"><span class="cl">        <span class="kt">int</span> <span class="n">lastIndex</span> <span class="o">=</span> <span class="o">-</span><span class="mi">1</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">        <span class="k">for</span> <span class="o">(</span><span class="kt">int</span> <span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="o">;</span> <span class="n">i</span> <span class="o">&lt;</span> <span class="n">len</span><span class="o">;</span> <span class="o">++</span><span class="n">i</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">            <span class="n">c</span> <span class="o">=</span> <span class="n">input</span><span class="o">.</span><span class="na">charAt</span><span class="o">(</span><span class="n">i</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">            <span class="k">if</span> <span class="o">(</span><span class="n">Character</span><span class="o">.</span><span class="na">isDigit</span><span class="o">(</span><span class="n">c</span><span class="o">)</span> <span class="o">||</span> <span class="n">c</span> <span class="o">==</span> <span class="sc">&#39;.&#39;</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                <span class="n">lastIndex</span> <span class="o">=</span> <span class="n">readDouble</span><span class="o">(</span><span class="n">input</span><span class="o">,</span> <span class="n">i</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">if</span> <span class="o">(</span><span class="n">lastIndex</span> <span class="o">==</span> <span class="o">-</span><span class="mi">10</span><span class="o">)</span>
</span></span><span class="line"><span class="cl">                    <span class="k">return</span> <span class="s">&#34;出错&#34;</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">                <span class="n">BigDecimal</span> <span class="n">number</span> <span class="o">=</span> <span class="k">new</span> <span class="n">BigDecimal</span><span class="o">(</span><span class="n">input</span><span class="o">.</span><span class="na">substring</span><span class="o">(</span><span class="n">i</span><span class="o">,</span> <span class="n">lastIndex</span><span class="o">));</span>
</span></span><span class="line"><span class="cl">                <span class="n">s2</span><span class="o">.</span><span class="na">push</span><span class="o">(</span><span class="n">number</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="n">i</span> <span class="o">=</span> <span class="n">lastIndex</span> <span class="o">-</span> <span class="mi">1</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">            <span class="o">}</span><span class="k">else</span> <span class="k">if</span> <span class="o">(</span><span class="n">c</span> <span class="o">==</span> <span class="sc">&#39;-&#39;</span> <span class="o">&amp;&amp;</span> <span class="n">i</span> <span class="o">==</span> <span class="mi">0</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                <span class="n">lastIndex</span> <span class="o">=</span> <span class="n">readDouble</span><span class="o">(</span><span class="n">input</span><span class="o">,</span> <span class="n">i</span> <span class="o">+</span> <span class="mi">1</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">if</span> <span class="o">(</span><span class="n">lastIndex</span> <span class="o">==</span> <span class="o">-</span><span class="mi">10</span><span class="o">)</span>
</span></span><span class="line"><span class="cl">                    <span class="k">return</span> <span class="s">&#34;出错&#34;</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">                <span class="n">BigDecimal</span> <span class="n">number</span> <span class="o">=</span> <span class="k">new</span> <span class="n">BigDecimal</span><span class="o">(</span><span class="n">input</span><span class="o">.</span><span class="na">substring</span><span class="o">(</span><span class="n">i</span><span class="o">,</span> <span class="n">lastIndex</span><span class="o">));</span>
</span></span><span class="line"><span class="cl">                <span class="n">s2</span><span class="o">.</span><span class="na">push</span><span class="o">(</span><span class="n">number</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="n">i</span> <span class="o">=</span> <span class="n">lastIndex</span> <span class="o">-</span> <span class="mi">1</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">            <span class="o">}</span><span class="k">else</span> <span class="k">if</span> <span class="o">(</span><span class="n">i</span> <span class="o">&gt;</span> <span class="mi">0</span> <span class="o">&amp;&amp;</span> <span class="n">c</span> <span class="o">==</span> <span class="sc">&#39;-&#39;</span> <span class="o">&amp;&amp;</span>
</span></span><span class="line"><span class="cl">                    <span class="o">(</span><span class="n">input</span><span class="o">.</span><span class="na">charAt</span><span class="o">(</span><span class="n">i</span><span class="o">-</span><span class="mi">1</span><span class="o">)</span> <span class="o">==</span> <span class="sc">&#39;(&#39;</span>
</span></span><span class="line"><span class="cl">                            <span class="o">||</span> <span class="n">isOperator</span><span class="o">(</span><span class="n">input</span><span class="o">.</span><span class="na">charAt</span><span class="o">(</span><span class="n">i</span><span class="o">-</span><span class="mi">1</span><span class="o">))))</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                <span class="n">lastIndex</span> <span class="o">=</span> <span class="n">readDouble</span><span class="o">(</span><span class="n">input</span><span class="o">,</span> <span class="n">i</span> <span class="o">+</span> <span class="mi">1</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">if</span> <span class="o">(</span><span class="n">lastIndex</span> <span class="o">==</span> <span class="o">-</span><span class="mi">10</span><span class="o">)</span>
</span></span><span class="line"><span class="cl">                    <span class="k">return</span> <span class="s">&#34;出错&#34;</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">                <span class="n">BigDecimal</span> <span class="n">number</span> <span class="o">=</span> <span class="k">new</span> <span class="n">BigDecimal</span><span class="o">(</span><span class="n">input</span><span class="o">.</span><span class="na">substring</span><span class="o">(</span><span class="n">i</span><span class="o">,</span> <span class="n">lastIndex</span><span class="o">));</span>
</span></span><span class="line"><span class="cl">                <span class="n">s2</span><span class="o">.</span><span class="na">push</span><span class="o">(</span><span class="n">number</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="n">i</span> <span class="o">=</span> <span class="n">lastIndex</span> <span class="o">-</span> <span class="mi">1</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">            <span class="o">}</span>
</span></span><span class="line"><span class="cl">            <span class="k">else</span> <span class="k">if</span> <span class="o">(</span><span class="n">isOperator</span><span class="o">(</span><span class="n">c</span><span class="o">))</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                <span class="k">while</span> <span class="o">(!</span><span class="n">s1</span><span class="o">.</span><span class="na">isEmpty</span><span class="o">()</span> <span class="o">&amp;&amp;</span> <span class="n">s1</span><span class="o">.</span><span class="na">peek</span><span class="o">()</span> <span class="o">!=</span> <span class="sc">&#39;(&#39;</span>
</span></span><span class="line"><span class="cl">                        <span class="o">&amp;&amp;</span> <span class="n">priorityCompare</span><span class="o">(</span><span class="n">c</span><span class="o">,</span> <span class="n">s1</span><span class="o">.</span><span class="na">peek</span><span class="o">())</span> <span class="o">&lt;=</span> <span class="mi">0</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl"><span class="c1">//                    double num1 = s2.pop();
</span></span></span><span class="line"><span class="cl"><span class="c1">//                    double num2 = s2.pop();
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>                    <span class="n">BigDecimal</span> <span class="n">num1</span> <span class="o">=</span> <span class="n">s2</span><span class="o">.</span><span class="na">pop</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">                    <span class="n">BigDecimal</span> <span class="n">num2</span> <span class="o">=</span> <span class="n">s2</span><span class="o">.</span><span class="na">pop</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">                    <span class="n">s2</span><span class="o">.</span><span class="na">push</span><span class="o">(</span><span class="n">calc</span><span class="o">(</span><span class="n">num2</span><span class="o">,</span> <span class="n">num1</span><span class="o">,</span> <span class="n">s1</span><span class="o">.</span><span class="na">pop</span><span class="o">()));</span>
</span></span><span class="line"><span class="cl">                <span class="o">}</span>
</span></span><span class="line"><span class="cl">                <span class="n">s1</span><span class="o">.</span><span class="na">push</span><span class="o">(</span><span class="n">c</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">            <span class="o">}</span> <span class="k">else</span> <span class="k">if</span> <span class="o">(</span><span class="n">c</span> <span class="o">==</span> <span class="sc">&#39;(&#39;</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                <span class="n">s1</span><span class="o">.</span><span class="na">push</span><span class="o">(</span><span class="n">c</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">            <span class="o">}</span> <span class="k">else</span> <span class="k">if</span> <span class="o">(</span><span class="n">c</span> <span class="o">==</span> <span class="sc">&#39;)&#39;</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                <span class="k">while</span> <span class="o">((</span><span class="n">tempChar</span> <span class="o">=</span> <span class="n">s1</span><span class="o">.</span><span class="na">pop</span><span class="o">())</span> <span class="o">!=</span> <span class="sc">&#39;(&#39;</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl"><span class="c1">//                    double num1 = s2.pop();
</span></span></span><span class="line"><span class="cl"><span class="c1">//                    double num2 = s2.pop();
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>                    <span class="n">BigDecimal</span> <span class="n">num1</span> <span class="o">=</span> <span class="n">s2</span><span class="o">.</span><span class="na">pop</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">                    <span class="n">BigDecimal</span> <span class="n">num2</span> <span class="o">=</span> <span class="n">s2</span><span class="o">.</span><span class="na">pop</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">                    <span class="n">s2</span><span class="o">.</span><span class="na">push</span><span class="o">(</span><span class="n">calc</span><span class="o">(</span><span class="n">num2</span><span class="o">,</span> <span class="n">num1</span><span class="o">,</span> <span class="n">tempChar</span><span class="o">));</span>
</span></span><span class="line"><span class="cl">                    <span class="k">if</span> <span class="o">(</span><span class="n">s1</span><span class="o">.</span><span class="na">isEmpty</span><span class="o">())</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                        <span class="k">return</span> <span class="s">&#34;出错&#34;</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">                    <span class="o">}</span>
</span></span><span class="line"><span class="cl">                <span class="o">}</span>
</span></span><span class="line"><span class="cl">            <span class="o">}</span> <span class="k">else</span> <span class="k">if</span> <span class="o">(</span><span class="n">c</span> <span class="o">==</span> <span class="sc">&#39; &#39;</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                <span class="c1">// ignore
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>            <span class="o">}</span> <span class="k">else</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                <span class="k">return</span> <span class="s">&#34;出错&#34;</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="o">}</span>
</span></span><span class="line"><span class="cl">        <span class="o">}</span>
</span></span><span class="line"><span class="cl">        <span class="k">while</span> <span class="o">(!</span><span class="n">s1</span><span class="o">.</span><span class="na">isEmpty</span><span class="o">())</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">            <span class="n">tempChar</span> <span class="o">=</span> <span class="n">s1</span><span class="o">.</span><span class="na">pop</span><span class="o">();</span>
</span></span><span class="line"><span class="cl"><span class="c1">//            double num1 = s2.pop();
</span></span></span><span class="line"><span class="cl"><span class="c1">//            double num2 = s2.pop();
</span></span></span><span class="line"><span class="cl"><span class="c1"></span>            <span class="n">BigDecimal</span> <span class="n">num1</span> <span class="o">=</span> <span class="n">s2</span><span class="o">.</span><span class="na">pop</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">            <span class="n">BigDecimal</span> <span class="n">num2</span> <span class="o">=</span> <span class="n">s2</span><span class="o">.</span><span class="na">pop</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">            <span class="n">s2</span><span class="o">.</span><span class="na">push</span><span class="o">(</span><span class="n">calc</span><span class="o">(</span><span class="n">num2</span><span class="o">,</span> <span class="n">num1</span><span class="o">,</span> <span class="n">tempChar</span><span class="o">));</span>
</span></span><span class="line"><span class="cl">        <span class="o">}</span>
</span></span><span class="line"><span class="cl">        <span class="n">BigDecimal</span> <span class="n">result</span> <span class="o">=</span> <span class="n">s2</span><span class="o">.</span><span class="na">pop</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">        <span class="k">if</span> <span class="o">(!</span><span class="n">s2</span><span class="o">.</span><span class="na">isEmpty</span><span class="o">())</span>
</span></span><span class="line"><span class="cl">            <span class="k">return</span> <span class="s">&#34;出错&#34;</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">        <span class="k">if</span> <span class="o">(</span><span class="n">result</span><span class="o">.</span><span class="na">toString</span><span class="o">().</span><span class="na">length</span><span class="o">()</span> <span class="o">&lt;</span> <span class="mi">20</span><span class="o">)</span>
</span></span><span class="line"><span class="cl">            <span class="k">return</span> <span class="n">result</span><span class="o">.</span><span class="na">stripTrailingZeros</span><span class="o">().</span><span class="na">toPlainString</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">        <span class="k">else</span>
</span></span><span class="line"><span class="cl">            <span class="k">return</span> <span class="n">result</span><span class="o">.</span><span class="na">round</span><span class="o">(</span><span class="k">new</span> <span class="n">MathContext</span><span class="o">(</span><span class="mi">6</span><span class="o">,</span> <span class="n">RoundingMode</span><span class="o">.</span><span class="na">HALF_UP</span><span class="o">)).</span><span class="na">toEngineeringString</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">    <span class="o">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="cm">/**
</span></span></span><span class="line"><span class="cl"><span class="cm">     * 获取是double值得最后一位索引
</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span>
</span></span><span class="line"><span class="cl">    <span class="kd">public</span> <span class="kd">static</span> <span class="kt">int</span> <span class="nf">readDouble</span><span class="o">(</span><span class="n">String</span> <span class="n">str</span><span class="o">,</span> <span class="kt">int</span> <span class="n">start</span><span class="o">)</span>
</span></span><span class="line"><span class="cl">            <span class="kd">throws</span> <span class="n">IllegalArgumentException</span><span class="o">{</span>
</span></span><span class="line"><span class="cl">        <span class="kt">int</span> <span class="n">len</span> <span class="o">=</span> <span class="n">str</span><span class="o">.</span><span class="na">length</span><span class="o">();</span>
</span></span><span class="line"><span class="cl">        <span class="kt">int</span> <span class="n">dotIndex</span> <span class="o">=</span> <span class="o">-</span><span class="mi">1</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">        <span class="kt">char</span> <span class="n">ch</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">        <span class="k">for</span> <span class="o">(</span><span class="kt">int</span> <span class="n">i</span> <span class="o">=</span> <span class="n">start</span><span class="o">;</span> <span class="n">i</span> <span class="o">&lt;</span> <span class="n">len</span> <span class="o">;</span> <span class="n">i</span><span class="o">++)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">            <span class="n">ch</span> <span class="o">=</span> <span class="n">str</span><span class="o">.</span><span class="na">charAt</span><span class="o">(</span><span class="n">i</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">            <span class="k">if</span><span class="o">(</span><span class="n">ch</span> <span class="o">==</span> <span class="sc">&#39;.&#39;</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                <span class="k">if</span><span class="o">(</span><span class="n">dotIndex</span> <span class="o">!=</span> <span class="o">-</span><span class="mi">1</span><span class="o">)</span>
</span></span><span class="line"><span class="cl">                    <span class="k">return</span> <span class="o">-</span><span class="mi">10</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">                <span class="k">else</span> <span class="k">if</span><span class="o">(</span><span class="n">i</span> <span class="o">==</span> <span class="n">len</span> <span class="o">-</span> <span class="mi">1</span><span class="o">)</span>
</span></span><span class="line"><span class="cl">                    <span class="k">return</span> <span class="o">-</span><span class="mi">10</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">                <span class="k">else</span>
</span></span><span class="line"><span class="cl">                    <span class="n">dotIndex</span> <span class="o">=</span> <span class="n">i</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="o">}</span> <span class="k">else</span> <span class="k">if</span><span class="o">(!</span><span class="n">Character</span><span class="o">.</span><span class="na">isDigit</span><span class="o">(</span><span class="n">ch</span><span class="o">))</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                <span class="k">if</span> <span class="o">(</span><span class="n">dotIndex</span> <span class="o">==</span> <span class="o">-</span><span class="mi">1</span> <span class="o">||</span> <span class="n">i</span> <span class="o">-</span> <span class="n">dotIndex</span> <span class="o">&gt;</span> <span class="mi">1</span><span class="o">)</span>
</span></span><span class="line"><span class="cl">                    <span class="k">return</span> <span class="n">i</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">                <span class="k">else</span>
</span></span><span class="line"><span class="cl">                    <span class="k">throw</span> <span class="k">new</span> <span class="n">IllegalArgumentException</span><span class="o">(</span><span class="s">&#34;不是数字，不能作为数字的一部分&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">            <span class="o">}</span>
</span></span><span class="line"><span class="cl">            <span class="k">else</span> <span class="k">if</span><span class="o">(</span><span class="n">i</span> <span class="o">==</span> <span class="n">len</span> <span class="o">-</span> <span class="mi">1</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">                <span class="k">return</span> <span class="n">len</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">            <span class="o">}</span>
</span></span><span class="line"><span class="cl">        <span class="o">}</span>
</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="o">-</span><span class="mi">10</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">    <span class="o">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="cm">/**
</span></span></span><span class="line"><span class="cl"><span class="cm">     * 判断优先级
</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="kd">private</span> <span class="kd">static</span> <span class="kt">int</span> <span class="nf">priorityCompare</span> <span class="o">(</span><span class="kt">char</span> <span class="n">op1</span><span class="o">,</span> <span class="kt">char</span> <span class="n">op2</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">        <span class="k">if</span><span class="o">(</span><span class="n">op1</span> <span class="o">==</span> <span class="sc">&#39;+&#39;</span> <span class="o">||</span> <span class="n">op1</span> <span class="o">==</span> <span class="sc">&#39;-&#39;</span><span class="o">)</span>
</span></span><span class="line"><span class="cl">            <span class="k">return</span> <span class="o">(</span><span class="n">op2</span> <span class="o">==</span> <span class="sc">&#39;*&#39;</span> <span class="o">||</span> <span class="n">op2</span> <span class="o">==</span> <span class="sc">&#39;/&#39;</span> <span class="o">?</span> <span class="o">-</span><span class="mi">1</span> <span class="o">:</span> <span class="mi">0</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="k">if</span> <span class="o">(</span><span class="n">op1</span> <span class="o">==</span> <span class="sc">&#39;*&#39;</span> <span class="o">||</span> <span class="n">op1</span> <span class="o">==</span> <span class="sc">&#39;/&#39;</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">            <span class="k">return</span> <span class="o">(</span><span class="n">op2</span> <span class="o">==</span> <span class="sc">&#39;+&#39;</span> <span class="o">||</span> <span class="n">op2</span> <span class="o">==</span> <span class="sc">&#39;-&#39;</span> <span class="o">?</span> <span class="mi">1</span> <span class="o">:</span> <span class="mi">0</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="o">}</span>
</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="mi">1</span><span class="o">;</span>
</span></span><span class="line"><span class="cl">    <span class="o">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="cm">/**
</span></span></span><span class="line"><span class="cl"><span class="cm">     * 这个函数能够判断是否是操作运算符
</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="kd">private</span> <span class="kd">static</span> <span class="kt">boolean</span> <span class="nf">isOperator</span> <span class="o">(</span><span class="kt">char</span> <span class="n">ch</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">        <span class="k">return</span> <span class="o">(</span><span class="n">ch</span> <span class="o">==</span> <span class="sc">&#39;+&#39;</span> <span class="o">||</span> <span class="n">ch</span> <span class="o">==</span> <span class="sc">&#39;-&#39;</span> <span class="o">||</span> <span class="n">ch</span> <span class="o">==</span> <span class="sc">&#39;*&#39;</span> <span class="o">||</span> <span class="n">ch</span> <span class="o">==</span> <span class="sc">&#39;/&#39;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">    <span class="o">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="cm">/**
</span></span></span><span class="line"><span class="cl"><span class="cm">     * 计算两个数的结果
</span></span></span><span class="line"><span class="cl"><span class="cm">     * 并返回
</span></span></span><span class="line"><span class="cl"><span class="cm">     */</span>
</span></span><span class="line"><span class="cl">    <span class="kd">private</span> <span class="kd">static</span> <span class="n">BigDecimal</span> <span class="nf">calc</span> <span class="o">(</span><span class="n">BigDecimal</span> <span class="n">num1</span><span class="o">,</span> <span class="n">BigDecimal</span> <span class="n">num2</span><span class="o">,</span> <span class="kt">char</span> <span class="n">op</span><span class="o">)</span>
</span></span><span class="line"><span class="cl">            <span class="kd">throws</span> <span class="n">IllegalArgumentException</span><span class="o">{</span>
</span></span><span class="line"><span class="cl">        <span class="k">switch</span> <span class="o">(</span><span class="n">op</span><span class="o">)</span> <span class="o">{</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="sc">&#39;+&#39;</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="k">return</span> <span class="n">num1</span><span class="o">.</span><span class="na">add</span><span class="o">(</span><span class="n">num2</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="sc">&#39;-&#39;</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="k">return</span> <span class="n">num1</span><span class="o">.</span><span class="na">subtract</span><span class="o">(</span><span class="n">num2</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="sc">&#39;*&#39;</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="k">return</span> <span class="n">num1</span><span class="o">.</span><span class="na">multiply</span><span class="o">(</span><span class="n">num2</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">            <span class="k">case</span> <span class="sc">&#39;/&#39;</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="k">if</span> <span class="o">(</span><span class="n">num2</span><span class="o">.</span><span class="na">equals</span><span class="o">(</span><span class="mi">0</span><span class="o">))</span>
</span></span><span class="line"><span class="cl">                    <span class="k">throw</span> <span class="k">new</span> <span class="n">IllegalArgumentException</span><span class="o">(</span><span class="s">&#34;除数不能为0&#34;</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">                <span class="k">return</span> <span class="n">num1</span><span class="o">.</span><span class="na">divide</span><span class="o">(</span><span class="n">num2</span><span class="o">,</span> <span class="mi">8</span><span class="o">,</span> <span class="n">RoundingMode</span><span class="o">.</span><span class="na">HALF_UP</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">            <span class="k">default</span><span class="o">:</span>
</span></span><span class="line"><span class="cl">                <span class="k">return</span> <span class="k">new</span> <span class="n">BigDecimal</span><span class="o">(</span><span class="mi">0</span><span class="o">);</span>
</span></span><span class="line"><span class="cl">        <span class="o">}</span>
</span></span><span class="line"><span class="cl">
</span></span><span class="line"><span class="cl">    <span class="o">}</span>
</span></span><span class="line"><span class="cl"><span class="o">}</span>
</span></span></code></pre></td></tr></table>
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